Adjustable dockboard with counterbalancing extension lip



G. McGulRE 3,203,002I

ADJUSTABLE DOGKBOARD WITH COUNTERBALANCING EXTENSION LIP Aug. 24, 1965 8Sheets-Sheet 1 Filed Dec. 7, 1964 w UWM w, M M M E@ m7 m Il? mise N N//Q//W/L l\ m x f www z L LN ma ME Nn Om Aw @Ww um u @v @En G. MOGUIREAug. 24, 1965 ADJUSTABLE DO CKBOARD WI TH GOUNTERBALANC ING EXTEN S IONLIP 8 Sheets-Sheet 2 Filed Dec. 7, 1964 Gem e MDEmz-'a 3,203,002.ADJUSTABLE DocKoARD WITH COUNTERBALANCING EXTENSION LIP Filed DGO. 7,1964 G. MCGUIRE Aug. 24, 1965 8 Sheets-Sheet 3 v@ Gear' e d.Mb Euwe 3 G.MCGUIRE ADJUSTABLE DOCKBOARD WITH COUNTERBALANCING EXTENSION LIP FiledDec. 7, 1964 8 Sheets-Sheet 4 Aug. 24, 1965 G. McGUlRE 3,203,002

ADJUSTABLE DOCKBOARD WITH COUNTERBALANCING EXTENSION LIP Filed Deo. 7.1964 8 SheetsSheet 5 \o O fs v LO LO Q Q m O /tl` v m \9 f `Q N Aug. 24,1965 G. McGUlRE 3,203,002

ADJUSTABLE DOCKBOARD WITH COUNTERBALANCING EXTENSION LIP Filed DeC. '7,1964 8 Sheets-Sheet 6 d mwd I A Eem-'gs Magnum G. MOGUIRE Aug. 24, 1965ADJUSTABLE DOCKBOARD WITH COUNTERBALANCING EXTENSION LIP 8 Sheets-Sheet7 Filed Dec. '7, 1964 Il ll llw y lllnld G. MCGUIRE Aug. 24, 1965ADJUSTABLE DOCKBOARD WITH COUNTERBALANGING EXTENSION LIP 8 Sheets-Sheet8 Filed DGO. 7, 1964 l m/awgd Gear s Ma' mrs 32 f MMJ' United StatesPatent u ADUSTAELE DQCKBGARD W'EH CUNTEB.-

BALANCEJS EXTENSN LE George McGuire, Thiensville', Wis., assigner toKeliey Company, Inc., liiilwauliee, Wis., a corporation of WisconsinFiled Dec. 7, 1964, Ser. No. 416,254

32 Claims. (Cl. lai- 71) This invention, like the Kelley Reissue PatentNo. 25,249, relates to adjustable dockboards adapted for installation onloading docks to span the gap between the dock and the bed of a truck orother carrier in position to be loaded or unloaded, and this applicationis a continuation-'in-part of application Serial No. 276,382, led April29, 196,3.

Dockboards of the type with which this invention is concerned have aramp which is hingedly supported at its rear edge upon supportingstructure Xed to the loading dock. An extension lip hinged tothe frontedge of the ramp hangs in a pendent position when the doclrboard is notin use and the ramp is in its so-called cross traffic position ush withthe door of the dock. This hinged extension lip is lifted to an elevatedposition forming substantially an extension of the ramp as the board isprepared for use, and when the doclrboard is in use this extension liprests upon the bed of the truck or carrier being loaded or unloaded.

The entire structure is set into a shallow pit in the dock with the rearhinged edge of the ramp flush with the top of the dock and the frontedge of the ramp adjacent to the front of the dock. From its crosstraffic position dush with the top of the dock, the ramp may be raisedor lowered to accommodate trucks of different iloor or bed heights.Biasing means, generally a group of heavy coil springs, acting through apivoted lever arm, at all times urges the ramp unwardly but isrestrained from' doing so by a manually releasable hold-down devicewhich is so constructed as to allow the ramp to float up and down withchanges in the height of the truck or carrier bed.

As in the Kelley et al. Patent No. 3,117,332 and the Pfleger et al.Patent No. 3,137,017, the extension lip is automatically lifted to anelevated position as the ramp j rises. The means by which this automaticelevation of the extension lip is effected includes a snap line,'i.e. aWire rope or cable having one end thereof connected to the stationarysupporting or mounting structure of the dockboard and its other endconnected to an actuating lever which forms part of the lip liftingmeans.

As the extension lip is thus automaticallylifted, a lip holding orsupporting means is automatically rendered operative to support the lipin a position somewhat short of its fully elevated position in whichlatter position it is substantially flush with the ramp. Thus, as theramp is lowered by the application of weight thereonfor instance, by anattendant walking out onto the ramp-the extension lip not only cornes torest upon the bed or oor of a carrier in position in front of thedockboard, but also moves'to its fully elevated position, which isfirmly defined, so that the ramp is supported at its front edge by thecarrier and the weight of the lip is removed from the lip supportingmeans, thereby allowing the latter to resume its inoperative condition.

Since the hinged extension lip is quite heavy, it obviously requiresconsiderable force to swing the same high enough to enable the lipholding or supporting means to be rendered operative to support the lipagainst dropping. Heretofore, this entailed rapid acceleration in theascent of the ramp so that the inertia of the lip as the ascent of theramp was suddenly stopped by the snap line connecting the lip liftingmechanism with the stationary mounting structure, could bring the lip toits required ddd Patented Aug. 24, 1955 ICC height, and to obtain thisneeded acceleration and consequent inertia, the ramp lifting springs hadto be quite strong; and, of course, the heavier the extension lip wasthe stronger the ramp lifting springs had to be.

In the smallelsizes of dockboards, this did not pose too serious aproblem, for in these smaller sizes the ramp lifting springs seldom hadto be so strong that a person of ordinary weight could not lower theramp by walking out onto it a short distance. But as the dockboardsincreased in size and the weight of the hinged extension lip becamecorrespondingly greater, a man of average weight could not lower theboard unless he walked all the way out to the front edge of the board.Hence, the means heretofore employed to lift the extension lip limitedthe size of these dockboards. It also limited the length and weight `ofthe lip, even in the smaller size dockboards.

This invention overcomes this objection and, for all intents andpurposes, removes the limitation upon the maximum size of dockboard thatcan be easily handled by a single attendant. The invention achieves itsobjective and purpose by counterbalancing a substantial portion of thegravity-produced moment of the extension lip about its hinged connectionwith the ramp, in such a Way that the counterbalancing force does notinterfere withA the lip assuming its pendent position and remaining inthat position when the board is not in use.

Stated in another way, one of the primary purposes and objects of thisinvention is to provide an improved adjustable dockboard of the typehaving an extension lip hinged to the front edge of the board or ramp,wherein the extension lip is counterbalance'd, but in such a way that,when the lip is in its pendent position, the effect of thecounterbalancing force upon the' extension lip is nullied; but as theextension lip` begins its upward swing, the counterbalancing meansincreases in eifectiveness.

It is also a feature and object of this invention to eliminate alldependence upon fast acceleration in the upward swing of the ramp andthe inertia of the eXtension lip, for the elevation of the lip to itslatched inter mediate position; and, instead, to provide a lip hftingspring which is strong enough, of itself, to lift the lip upon releaseof the energy stored in' the spring', together with a novel manner ofloading or energizing the spring during lowering of the ramp, so thatthe spring may be loaded and secured in a loaded or energized conditionby releasable latch means.

With this way of lifting the extension lip, the ramp can be raised withthe'lip in its pendent position, and then by simply releasing the storedenergy ofthe spring, bring the lip to its latched position. Elevatingthe eX- tension lip in this manner has the advantage of reducing theheight to which the ramp must be raised in preparing the dockboard foruse. ,y

Heretofore the latch mechanism by which the lip was supported in anelevated position acted upon the lip through a relatively short leverarm; in fact this was the case in those embodiments of this inventionwhich were disclosed in the aforesaid application Serial No. 276,382.Because of this, small deviations` from prescribed clearance tolerancesresulted in largeV variations in the angle at which the lipV wassupported, and also made engagement of the latch mechanismA somewhatunreliable.

With a view towards overcoming the objections of past lip supportingdevices, this invention has another of its objects to provide a lipsupporting latch device which acts upon the lip through a much longerlever arm and hence is not nearly as critical in its clearance tolerancerequirements.

Ordinarily when a truck backs into place in front of a dockboard whichhas been raised and has its lip elevated,

the doors of the truck are open and the lip simply protrudes into thetruck. There are times, however, when for one reason or another, thetruck collides with the extended lip. t To prevent damage tothedockboard when that happens, this invention has as another` of itsobjects to provide yieldability in the lip supporting means whereby thelip will fold down if force is applied against it as when a truck vbeingbacked into position collides with it.

With the above and other objects in view which -will appear as thedescription proceeds, this invention resides in the novel construction,combination and arrangement of parts substantially as hereinafterdescribed and more particularly defined by the appended claims, it beingunderstood that such changes in the precise embodiment of Vthe hereindisclosed invention may bemade as come within the scope of the claims.

The accompanying drawings illustrate several complete examples of thephysical embodiments of the invention, constructed according to the bestmodes so far devised for the practical application of thefprinciplesthereof, and in which: Y

FiGURE 1 is 4a longitudinal sectional view through an adjustabledockeoard installation, embodyingthis invention and illustrating theramp in its cross trafiic po-` sition, with the extension position; Y V

FIGURE 2 isran enlarged fragmentary cross sectional yview throughtherfront end portion of the ramp and the extension lip, illustratingtheV ramp raised and the extension lip in its intermediate supportedposition, preparatory to being lowered onto the bed'of a truck or othercarrier in position in front of the dockboard,

FIGURE 3 is a cross sectional View similar to FIG-y URE 2 but showingthe ramp lowered and the extension lip resting upon the bed of the truckor carrier;

FIGURE 4 is a detail sectional View through the front endV portion ofthe ramp and extension 1ip, on a plane lip hanging in its pendent spacedlaterally from that of VFIGURE 1;

FIGURE 5 is a perspective view of a portion of the dockboard,tobetterfillustrate the structure by which the extension lipis lifted toand supported in its in- Itermediate or partially raised position;V

FIGURE 6 is a longitudinal sectional view through a dockboardinstallation, illustrating that embodiment Vof the invention whereinelevation of thefhinged extension lip is effected solely by the releaseof energy storied Vin the counterbalancing spring, said view showing theramp Vin its elevated condition, and the extension lip lifted;

FIGURE 7 is a view similar to FIGURE 6, but'showving the ramp Vin apartiallyv lowered condition and the extension lip intits pendentposition; V

FIGURE 8 is a sectional view through the ramp and itshinged extensionlip, illustrating another embodiment of this invention equipped with theimproved lip support which permits greater latitude in clearancetolerance and incorporates protection against Vdamage by trucks backinginto the extended lip; y V

FIGURE 9 is aY-detail cross sectional view through- FIGURE 8 on theplane of the line 9-9; p

FIGURE 10 is a fragmentary detail sectional View through FIGURES ontheplane of the` line 11i- 10; FIGURE 11 is a viewsimilar toV FIGURE 8, butillustrating the ramp infits raised condition, and the hinged Vlipelevated or extended;

FIGURE 12 is a view similar to FIGURE l1 showing how the.4 lipsupporting means yields to prevent damage toY the dockboard in the eventa truck backs intorthe extend- 'ed lip;V Y

FIGURE 13 is a view 'similar to FIGURE V11, but illustrating a slightlymoditied embodiment of the lip 'support; and i i FIGURE 14 is asectional View through the front end post of the ramp and its hingedlip,illustrating another adaptationof the improved lipsupport;

may be constructed in any suitable manner but is pref-- erablyfabricated from structural steel. 1t has parallel front and rear members5 and 6 connected by parallel rails 7, only one ofvwhich is shown. Atits rear, the supporting structure has a plurality of upright members 8-again only one of which is shown-which collectively support a crossmember 9 to which the rear edge of a ramp structure, indicated generallyby the numeral 10, is hingedly connected, as at 11. t

vThe rampstructure 1t), like the stationary supporting structure ispreferablyv built of structuralsteel, and includes a plurality ofparallel longitudinal rails 12-only one of which is shown-and a steelplate orV deck 13, welded or otherwise secured to the rails 12. At itsfront edge, theramp has an apron or rail 14 depending from its deck 13`and welded or otherwise secured to the longitudinal rails 12. For apurpose to be described, the front rail has a hole 15 medially of itsends and an outwardly loffset bridge piece 16 defining the bottom ofthis hole.

At its rear edge, the ramp has an angle iron cross member 17 which issecured to the rails 12, and to the underside of the deck, the hingeconnection 11 having one of its complementary parts secured to thisangle iron cross rail 17. t

An extension lip 18'is` hinged to the front edgeof the ramp, as at 19,to swing from a pendentfposition to an elevated working or operativeextended position forming substantially an extension or continuation ofthe deck 13 of the ramp.V The hinge 19 which connects the extension lipwith the front edge portion of the ramp consists of lengthwiseinterposed tubes 20 and 21, which are re- .specti'vely fixed to theunderside of the lip and to the apron or front rail 14, and a hinge pinor pintle 22 received in these tubes.

The hinge 19 is of the knuckle joint variety, since the rear edge of thelip engages the front edge of the ramp deckand prevents furtherelevation of the lip whenthe lip is in its fully raised or elevatedworking position forniing an extension of the ramp. Accordingly, in use,when the hinged lip comes to rest upon the bed of a carrier `(indicatedat B in broken lines in FIGURES 2 and 3), the ramp will be supportedatits front by the carrier.

'When the dockboard is Vinstalled on a loading dock 23, the entirestructure is set into aV shallow pit-24 formed in the dock, with thehinged rear edge of the ramp ush with the top of the dock and its frontedge adjacent to the front of the dock. Hence, the ramp may occupy acrosstraffic position flush with the'top of the dock, as shown in FIGURE1, and may be tilted downwardly, if necessary, to accommodate a truck orother carrier, the bed or floor of which istbelow dock level; or it maybe raised to a substantial angle above dock level. Y

Y The ramp is supported in its cross-traffic position by legs 25depending from its front end portion to rest upon pedestals 26 at thefront end of the supporting structure, therebeing two such hinged legsand two pedestals, ,one wpair thereof at each side of the ramp. Y

`The legs25 and the manner in which they lfunction to support the rampin its cross-trafiic position, and even in a position beloW-dock-level,constitutes'tne subject matter V of the aforesaid Pfieger et al. PatentNo.V 3,137,017, issued June 16, 1964, to the assignee of this invention.Y The ramp is biased upwardly by means of a group of heavy tensionsprings 27, only one of which is shown, anchored at one end to themounting or supporting struc- `ture 4 and having their other endsconnected to a lever arm 28. One end Vof* the arm 28'is'hingedlyconnected to the stationary supporting structure, as at 29; its otherend bears against the bottom edge of a cam plate` 3) fixed to theunderside of the ramp. Hence, the springs 27 acting through the pivotedlever-arm 28 and the cam4 plate 3f) impart an upward thrust or bias uponthe ramp tending at all times to raise the same to an upwardly inclinedposition projecting a substantial distance above dock level.

However, the ramp may be held in any lowered position by means of ahold-down device, indicated generally by the numeral 3l. This hold-downdevice may be like the one shown inthe aforesaid Patent No. 3,137,017.In any event, it is manually releasable by pulling upwardly upon areleasing arm 32. This may be done by means of a releasing cable or cord33 connected to the arm and having a linger ring 3d accessible fromabove the deck of the ram-p.

As noted hereinbefore, when the hold-'down device 31 is released and theramp is raised by the springs 27, the hinged extension lip i8 isautomatically swung to an intermediate elevated position somewhat shortof its fully elevated position, where it is supported by a lipholding orsupporting device indicated` generally by the numeral 3S. In theembodiment of the invention illustrated in FIGURES 1 -to 5 inclusive,this lip supporting or holding device 35 comprises a pawl or latch 36and an abutment 37 on one of the hinge-forming tubes Ztl which are fixedto the extension lip. The pawl or latch 36 is pivotally mounted upon theunderside of the ramp in any suitable manner, as by a'pin 3S whichpasses through the hub of the pawl or latch, and a pair of ears 39 xcdto the underside of the ramp and between which the pawl is received, andin its operative position projects through the hole to engage theabutment 37.

The weight of the pawl or latch is so distributed about its pivotalmounting that it normally hangs in an inoperative position outside theorbit of the abutment 37. Means to be hereinafter described are providedfor swinging the pawl to its operative position.

The structure thus far described, yessentially is no part of the presentinvention, but its description is at least helpful and perhaps necessaryfor an understanding of the invention. l

The manner in which the hinged extension lip is lifted constitutes oneof the primary features of this invention. Because of it:

(l) The weight and size of the extension lip can be practicallydisregarded in designing the dockboard,

(2) yPrevious limitations upon the maximum size of the board are largelyremoved, and

(3) Softer, less powerful ramp lifting springs may be employed toelevate the ramp, thus eliminating much' of the shock to the structureand making it easier to lower the ramp.

The structure for lifting the hinged extension lip comprises arelatively short lever arm or finger dit, rockably mounted on the rampin front of the hole 15 in its front rail, to swing about an axisparallel to the hinge axis of the lip and preferably coinciding withthat `axis. rthus the short arm or finger et? maybe pivoted upon thepintle 22, the adjacent tubes Ztl and 21 beingV spaced rom one anotherto accommodate the same.

Rocking the arm or finger counterclockwise, as viewed in FIGURES l and2, causes it to bear against the underside of the extension lip and liftthe same. Such motion is imparted to the arm or linger 4t? by a downwardpull upon a lever arm di, which is xed with respect to the arm or fingerdit and preferably is integral therewith. Together the short arm oriinger al@ and the longer lever arm 41 may be considered a bell cranklever, and the angular relationship between them is such that when theextension lip hangs in its pendent position the arm il occupies asubstantially horizontal position at the underside of the ramp; and whenthe extension lip is in rits intermediate position shown in FIGURE 2,the arm l is spaced a slight distance from the rear of the offset bridgeportion 16 of the front rail 14, though it may have contacted the bridgeportion when the ramp reached its uppermost position and just before thesupporting means 6 35' was activated and the weight of the lip wasapplied thereto.

The forwardly offset bridge portion 16 not only extends across and formsthe lower edge of the hole 15 in the rail 14 to reinforce the rail atthis point, but, as will be seen, it also provides protection for thearm 421. oi the bell crank lever and the adjacent parts. Y

A snap line 44 having one end connected with the free end of the arm 41and its other end connected through a tension spring 45 with thestationary supporting structur-e 4, is drawn t-aut as the ramp iselevated by its springs 27 and, in so doing, pulls the arm 41 from itssubstantially horizontal posi-tion beneath the ramp downwardly to itssubstantially vertical position shown in FIGURE 2. This, of course,swings the extension lip about its hinged mounting toward its elevatedposition, and far enough for the pawl or latch 36 to engage the`abutment 37.

A feature of this invention is that elevation of the extension lip iseiected not only by the tightening of the snap line and the consequentsudden interruption of the elevation of the ramp with its attendantinertia effect upon the lip, but also by a counterbalancing means,indicated generally by the numeral 46 and 'by which a major portion ofthe gravity-produced moment of the extension lip is borne duringelevation of the lip.

In the embodiment of the invention illustrated in FIG- URES 1 through 5,the counterbalancing means 46 comprises a relatively heavy compressionspring 47 reacting between the ramp and the arm 41 which, as will appearhereinafter, can also be considered a crank arm. One end of the spring47 bears against an abutment 48 ixed to the underside of the ramp. Thisabutment may be simply one flange of an angle iron welded to one of the'rails 12, with a hole 49 in which one end-.portion of a rod Sti isslidably received. The rod 50 passes lengthwise through the spring andhas stop nuts Sl threaded on its front end portion to provide anabutment for the other end of the spring, it being understood that thefront end portion of the rod is screw threaded.

The front end of the rod 5t) has a clevis 52 formed thereon or fixedthereto, to embrace the free end portion of the arm 41 and be pivotallyconnected thereto by a pin 53.- It follows, therefore, that the force ofthe compressed spring 47 reacting between the i-xed abutment 4g on'theunderside of the ramp and the free end of the arm 41, imparts torque tothe arm, providing the arm is not on dead-center, that is, that itspivoted connection 53 with the rod is not directly on a straight lineintersecting the axis about which the arm 4l turns and coinciding withthe thrust axis of the spring.

The relationship of these parts is thus comparable and quite similar tothat of a crank motion and, for this reason, the arm 41 may beconsidered a crank or moment arm. Also, when the arm 41 is in itssubstantially horizontal position beneath the deck of the ram (whichposition it occupies when the lip hangs in its pendent position) the armand the rod 50, in etect form a toggle. If this toggle is directly ondead center, the spring cannot impart torque to the arm in eitherdirection, and therefore cannot in anywise interfere with the positionof the extension lip, so that the latter canl hang freely in its pendentposition. But to assure that the spring will not keep the lip fromassuming and maintaining its pendent position-when this should be itsposition-it is preferred that the toggle be slightly broken in theupward direction or', in other words, that the arm 4l be slightly beyonddead center when the lip is in its pendent position. Thus, the parts areso proportioned and designed that before the clockwise motion of the arm41 is arrested by its collision with the underside of the ramp, itsconnection 53 with the rod 50 crosses dead center.

Obviously, of course, as soon as the crank arm 41 begins to rotate in acounterclockwise `direction about its pivotal mounting in response to apull exerted thereon by the snap line 44 and said connection 53 crossesdead effectiveness of the spring.

Since the hinged extension lip must be free to drop back to its pendentposition when the truck or carrier pulls away, ittollows that thecounterbalancing means, i.e. the spring 47, must not balance the fullweight of the extension lip. Accordingly, the adjustment of the springtension should be such that while a major portion -of thegravity-produced moment of the extension lip is counteracted by thecounterbalancing spring during elevation of the lip, itshould definitelynot be that entire moment. In practice it ,has been found advantageousto have the spring adjustment such Vthat approximately eighty percent(80%) of the gravity-produced moment of the extension lip about itshinge axis is carried by Y the counterbalancing spring. Y

With this adjustment of the spring force, the extension Ilip dropsreadily but in a cushioned manner Yto its pendent position as thecarrier pulls away from under it. Preferably the pendent position of theextension lip is defined by the engagement of the lip with a pluralityofrubber bumpers S mounted on the front rail 14, one of Vthe bumpersbeing shownin FIGURE 4. t

Although the connection between the snap line 44 and the crank arm 41maybe, effected in any desired manner, it is convenient to attach thesnap line to a cross pin 56, which passes through the arms of theVclevis 52. Y

The pawl or latch 36 is moved from itsY inoperative i position to itsoperative position "in time to dispose its free-end behind the lug orabutment A37 by a tensionY spring 57 connected between the snap line 44and the pawl or latch rearwardly of its Vpivot 39. Thusas the snap lineisdrawn taut, the spring, 57 pulls the lpawl 36 into its operativeposition. v

As shown in FIGURESS and 7, this invention also lends itself toadaptation inV a form Vwhich completely obviates the needfor any liftingforce beingapplied to the extension lip in consequence of elevation ofthe ramp. Forrthis purpose, means are provided'to load or Ycompress vthespring 47 during descent of the ramp, and'latchV 'means, indicatedgenerally by the numeral l6i), serves Ato hold the spring in its cockedor loaded condition until the lip isV to be lifted.V To cock or loadthev spring, Vthe end of the rod 50' which extends lengthwise throughthe -spring and slidably through-.vth'elhole Vin the VXedfabut-v ment 48is connected by means of a cablev 61 to the ramp raising lever arm 28,the cable Vbeing trained over a sheave 62 mounted at the underside ofthe'ramp near its hinged rear edge. i 1 Y As will.be readily understoodfrom a comparison of lFIGURES 6 and 7, as the ramp is lowered by theattendant walking out on Yto it, or othewise, the arm 23 swings forwardand thus exerts a pull on the cable 61. AThis draws therod 50' back tocompress the spring,

and when the spring has been compressed the latch deviceY 60 is engaged.With the latch device thus engaged, and the spring 47 cocked orv loaded,the extension lip is in its pendent position inY which position itremains sequence of release of the hold-down device, and until the latchis disengaged.. Thelatch device 60 maytake any suitable form and, forpurposes of illustration, has

been shown as an abutment 63 iixed to ther rod 50' and a spring pressedinger or Y'bolt 64 pivoted to theunderside of the ramp with its free endbiased upwardly to lie in the path of the abutment 63 andV snap in ifront -of it as the abutment moves rearwardly past it. Dise engagementof the latch can be eiected in any suitable manner, asby simply pullingdown on the bolt 64, but Vit`fis preferable to etect this releaseautomatically as the rampv swings up. To do so, a snap line 65 isconnected between the bolt'64` and the stationary supporting structure,as shown.

With the release of the latch, the force stored in the Vspring shiftsthe rod Sti forwardly, Which-being connected to the crank arm 41-liftsthe extension lip. It should be understood, however, that in this formof the -invention the crank arm 41 must not be permitted to swing to adead center position for otherwise the release of the spring force couldnot impart torque to the arm 41', as needed to lift the extension lip.

The embodiment of the invention illustrated in FIG- URES 8-12,Vinclusive, is distinguished lby the fact that it combinescounterbalancing of a substantial portion of the gravity-produced momentof the lip with an improved lip supporting mechanism, which not onlyaiords greater latitude in the clearance tolerances required to 'assurereliable engagement ot` the lip supporting latch means, but alsoprotects the structure against damage in the event a truck accidentallybacks into the lip when the latter is in its extended or elevatedposition.

As Yin Ythe embodiment of the invention illustrated in FIGURES l-5,inclusive, the lip is elevated by a downward pull on a crank arm 141which in this case has the lip lifting nger 140 formed integraltherewith, thelip lifting-motion being applied to the arm by thetightening of a snapv line 144 as the ramp is raised. Also, as in theearlier described embodiment of the invention, a spring 69 reactingbetween a xed abutment on the ramp and the free end of the crank arm 141assists in elevating the lip, but in this instance the rod onrwhich the(counterbalancing spring is mounted is not simply one solid unit butrather consists ofjfront end rear telescoped sections 70 and 71. Therear section 71, sa tube and has the front section 70, which is simply arod with'its front endrportion threaded, slidably received therein. vTheextreme rear end of the tube 71 is closed, as at 72;,and confinedbetween the closed end 72'of the tube and the rear end of the rod 70 isa compression spring 73. This yieldingly tends to separate thetelescoped sections and normally maintains the composite rod structureat its maximum length, which is defined bythe engagement of a pin 74fixed to the rod,

Vwith the front end of a slot 7S in the wall of the tube.

VThe rear end portion of the tube 71 is slidably received in a guide orVsupportr 76 Xed to the underside of the ramp and whichA may consistsimply of a hole inone flange of an angle iron welded or otherwisesecured to the ramp.V This guide '76 also serves as an abutment for thecounterbalancing spring 69 which surrounds the sleeve and has its frontend bearing againstV an abutment 7,7 adjustably secured to the threadedrod 7i).v

Accordingly, the springs 69 performs the same counter- Abalancingfunction as the spring 47 in the previouslyV l described embodiment ofthe invention and, as in that embodiment, the spring 69 carriesapproximately eighty percent (80%) of the gravity-produced moment of they lip about its hinge axis.

YWhen the ramp is raised and the snap line 144 vbecomes taut, the arm141 is pulled down toward its operative position and inpso 'doingelevates the lip with 'even duringl elevation of the ramp by itsspringsin conthe .assistance of the spring 69. During this operation vtheYtelescoped rod structure of course moves endwise in a forward directiondrawing its rearmost end portion Vcompletely out of a hole 79 in a crossrail 80 in which hole the rear end portion .of the tube is slidablyreceived. The raising of the ramp 'also moves a latchplate or stopdevice S1 whichispivoted, as at 82, to the cross Ymember 80, into anoperative position closing the hole 79 and blocking Vrearward movementof the tube 71. The latch plate 81 normally hangs in an inoperativeposition, as shown in FIGURE 9, but is swung to its operative of theirpermitted extension.

9 position by the tightening of a snap line 83 which has one end thereofconnected to the latch plate and its other end suitably secured to thestationary structure. A spring 84 is preferably connected in series withthe snap line.

Since the two springs 69 and 73 together support more than the entiregravity-produced moment of the lip, it yfollows that when the parts arein their positions shown in FIGURE 11 and the lip is in its elevated orextended position, the combined spring forces will be suiiicient to holdthe arm 141 in its operative lip supporting position. However, in theevent of the application of an external force on the edge of theextended lip, as when a truck-shown in dotted lines in FIGURE12-accidentally backs into the lip, both springs will yield and permitthe lip to be folded down before damage to any part of the structuretakes place.

An especially signiiicant and ladvantageous aspect of the lip supportillustrated in FIGURES 8-12, resides in the fact that it acts upon thelip through a relatively long lever arm-namely, the full length of thearm 141. In practice, this is at least six inches (6") which compareswith approximately one inch (1") to one and one-half inches (l1/2) forthe effective length of the'abutment 37 in that form of the inventionshown in FIGURES 1-5. Accordingly, relatively wide latitude in theadjustment of clearance tolerances is permitted, for, as will be readilyapparent, even relatively significant diierences in the overall lengthof the telescoping rod, from its pivotal connection with the arm 141 toits rearmost end 72, will not seriously etect the angle at which the lipis supported when the rear end of the rod bears against the latch plate81. It is thus entirely feasible to provide adequate clearance betweenthe front face of the latch plate S1 and the adjacent rear end 72 of therod to enable the latch plate 81 to be swung into its operative positionas the lip is elevated. The adjustment ot this length is readilyeffected by having the clevis 52 by which the front end ofthe rod isconnected to the arm 141 threaded onto the rod 70 and locked in place bya lock nut 85. This adjustment should be such that when the rear end 72of the telescoped rod bears against the latch plate S1, as shown inFIGURE 1l to support the lip in its elevated position, sutlicientclearance remains between the arm 141 and the bridge 16 to provide forthe necessary additional motion of the pivoted arm and telescoped rod toassure free positioning of the latch plate during elevation of the lip.

As will no doubt be readily understood, the advantages which flow fromhaving the lip support act upon the lip through a relatively long leverarm and the consequent freedom to provide adequate clearance between thefront face of the latch plate 81 and the adjacent rear end of the rodupon which the counterbalan'cing spring 69 is mounted, are in nowisedependent upon the telescoped two part formation of this rod and thespring 73 which yieldingly holds the two sections of the rod at thelimit In other Words, these advantages are equally inherent in and justas significant in the structure shown in FIGURE 13 which differs fromthat of FIGURES 8-12 only in the substitution of a solid one-piece rodSti for the telescoped two-part rod Til-71 and, of course, the omissionof the spring 7?.

A simplified version ofthe improved lip support is illustrated in FIGURE14. In this case the lip lifting and supporting crank. arm 9@ is held inits operative position by a latch lever 91, which is pivoted as at 92von an adjacent portion of the ramp, toswing from an inoperative positionto whichV it is biased by its own weight distribution to its operativeposition shown in FIGURE 14. If desred, the operative position of thelatch lever 91 can be defined by a stop 93 on the crank arm. A snap line94 connected between the lever 91 and the stationary structure of thedockboard serves to swing the latch lever 1G to its operative positionas the ramp is raised and the lip is lifted.

Upon lowering of the ramp and the engagement of the lip with the bed ofa truck or carrier, the latch lever 91 swings to its inoperativeposition out of the orbit of the crank arm 9i?, which is then free toreturn to its inoperative position when the lip drops to its pendentposition.

Although in the structure shown in FIGURE 13, elevation of the lip isnot spring assisted, it will be obvious that this feature could be addedif desired. It will also be evident that the advantage of having the lipsupporting reaction applied to the crank arm near its outer end so thatthe full length of the arm is utilized and wide latitude in clearancetolerance is achieved, is equally present whether the arm is supporteddirectly by the lip supporting latch, as in FIGURE 14, `or indirectlythrough a rod as in FIGURES 8-13. In each case it is theinterpositioningl of supporting structure between portions of the crankarm and the ramp which are spaced from the pivot axis of the arm, whichserves to hold the arm in its operative lip supporting position.

From the foregoing description taken in connection with the accompanyingdrawings, it Will be readily apparent to those skilled in this art thatthis invention provides a signiiicant improvement in adjustabledockb'oards of the type with which this invention is concerned, since bycounterbalancing the extension lip in the way it is, only a smallproportion of the gravity-produced moment of the lip must be overcome bythe ramp raising springs. The limitations heretofore imposed upon thesize of the dockboard by the manner in which the extension lip waslifted are thus entirely overcome. It will also be apparent that themanner in which the lip is counterbalanced to assist in the elevationofthe lip is in nowise dependent upon the form of the lip raisingmechanism, being just as etico-tive whether the lip raising means is ofthe automatic snap line variety employed in the structure shown inFIGURES 1 to 5, inclusive, or of the manual variety, as in ReissuePatent No. 25,249, or in any other suitable form.

Those skilled in the art will also appreciate the advantages of havingthe lip support act upon the lip through a relatively long lever ann;and of leaving the lip in its pendent position as the ramp is elevatedas in the modified embodiment of the invention shown in FIGURES 6 and 7,wherein the lifting of the lip is completely `divorced from the raisingof the ramp. l

What is claimed as my invention is:

1. In an adjustable -dock'board of the type wherein' a ramp having frontand. rear edges has its rear edge hingedly supported so that the rampmay swing up and down about its rear edge, and has an extension liphingedly connected to its front edge for movement between a pendentposition with respect to the ramp and an elevated position formingsubstantially an extension of the ram-p, the improvement whichcomprises:

(A2 energy storing means to countei'balance a portion of thegravity-produced moment of the extension lip about its hinge connectionwith the ramp;

(B) means operatively connecting the energy storing :means with theramp; and

(C) means operatively connecting the energy storing means with theextension lip, whereby the energy storing means reacts between the rampandthe extension lip to impart lifting torque to the extension lip, saidlast named means including structure having a moment arm through whichthe energy storing means exerts its counterbalancing force upon theextension lip, movement of the extension lip to its pendent positionmoving said moment arm into substantially its dead center position tothereby substantially nullify the effect of the energy storing meansupon the exten-sion lip, and said moment arm being operative to renderthe counterbalancing effect 11 Y of the energy storing means upon theextension lip increasingly effective as the extension Ilip moves fromsaid pendent positionrtowards ,its elevated position. a

2. In an adjustable dockboard, the combination of claim 1 wherein sai-dstructure which provides the moment arm is a crank arm mounte-d to swingin a plane normal to the hinge axis of the extension lip.

3. In an adjustable dockboard, the combination of claim 2, Y

wherein the crank arm is located at the underside of the ram near thefront end thereof, and wherein a push rod mounted under the ramp forendwise move- 1 ment towards and from the front end yof the rampconnects the energy storing means and the crank arm,

one end of the push rod being connected with the energy storing meansand the other end of the push rod being connected tothe crank arm. Y 4.In an adjustable dockboard of the type wherein a ramp having front andrear edges has its rear edge hingedly supported so that the ramp mayswing up and down about its rear edge, .and has an-extension liphingedly connected to its front edge for movement between a pendentposition with respect to the ramp and an elevated position formingsubstantially anextension of the ram-p, the'improvement which comprises:

(A) spring means strong enough to counterbalance a substantial portionof the gravity-produced moment ofthe extension lip about its hingeconnection with the ramp; i

(B) an anchor for with respect to the ramp; Y

(C) a crank arm mounted to turn about an axis fixed with respect to theramp;

(D) rneans'through which the gravity-produced moone end of the-springmeans fixed ment of the extension lip -is impose-d u-pon the crank armand tends to'turn the crank arm in one direction;

Yand Y (E) means forming a pivoted force transmitting connection'between the other end of the spring means .and the crank arm'andthrough which the force of y the spr-ing means/acts when the crank armis not on; dead center to impart lip lifting torque tothe cranky arm,the crank arm being substantially on Adead center when Vthe extensionlip is in said pendent position. i Y

5. In an adjustable dockboard, thestructure of claim VIl, furthercharacterized by the Yfact that said pivoted force transmittingconnection between the spring and the crank arm occupies a positionslightly beyond dead center'when the extension lip is in its pendentposition. i

6. Inan adjustable dockboarcL'the structure of claim 4,

further characterized by: a

(A) stationary supporting structure to which the rear edge of the rampis hingedly connected;

l2 "(B) the'lip' lifting means offclaim' Vincludes Va snap lineconnected tothe stationary supportingvstructure to activate the lip"lifting means as the ramp rises. 8. The adjustable dockboard of claim d,wherein said spring means is strong enough to counterbalance the entiregravity-produced'moment ofthe extension lip, and further characterizedby: L 5

(A) stationary supporting structure upon which the v rear edge of theramp is supported; Y

(B) manually A'releasable biasing means reacting between the stationarysupporting structure and the ramp to swing the ramp upward when saidbiasing means is released, with a force that can be overcome by theYapplication of weight upon the raised ramp,

said biasing means including a part which moves with respect to thestationary supporting structure and the ramp as the ramp is raised and/or lowered; Y

(C) spring loading means connected with said part and ywith the end ofthe :spring means which is connected with the crank arm, to load lthespring means as said part moves in consequence of lowering of the'ramp;

(D) releasable latch means carried by the ramp and operable to hold thespring means in its loaded condition, so that the ramp may be raisedwith the extension lip in its pendent position; and v (E) meansto-release thelatch means. v 9. 'The adjustable dockboard of claim S,wherein the Ymeans torelease the latch means includes a snapline havingkone end fixed to thestationary-supporting structure and itsotherendconnected with the latch means to effect release of the latchmeans-when the snap line becomes taut, so that the latch means isVautomatically released to allow the loaded spring to swing the extensionlip towards its elevated position when the rampr'has been raised to apredetermined height. Y Y

10. I n an adjustable dockboard of thetype wherein a vramp -having frontand rear edges has its rear edge hingedlysupported so thatthe ramp mayswing up and down about its rear edge, andahas'an extensionlip hingedlyconnected to its front edge for movement between a pendent position withrespect to the ramp and an elevated position forming'substantially anextension of the ramp, the im- Y `prox/ement which comprises:

(B) releasable lip supporting means on the ramp operable to support theextension lip in an intermediate position short of its fully elevatedposition'when the n,

lip has been lifted to said intermediate position; and

(C) lip lifting means operatively connected with the stationarysupporting structure, the ramprand the ex- Y tension lip and operable inconsequence of movement ofthe ramp about its hingedconnection with thestationary supporting structure, to `impart initial lipv lifting motionto the crank arm and with the help of the spring means to lift theextension lip far enough to Y enable the lip supporting means to becomeoperative. '7. The adjustable dockboard of claim 6', furthercharacterized by:

'(A) manually releasable biasing means reacting between the stationarysupporting structure and the ramp to swing the ramp upward when saidbiasing means is released; and wherein Y (A) means to counterbalancearportion ofthe gravity- .produced moment of the extension lip about itsf hinge connection with the ramp; and v (B) means operatively connectingsaid connterbalanc- Y ing means with the ramp and with theV extensionlip Vand-through which the counterbalancing mean'sre- Vacts between theramp and the extensionlip to impart lifting torque to the extension lipas the extension lip moves from said pendent position towardsV itselevated position, Y Y

arm through which'the force of the'counterbalancing meansis translatedinto lip lifting torque of increasing yeffectiveness as the extensionlip'appreaches its elevated position, said moment arm beingsubstantially on dead center when the ex- Y tensionlip is in saidpendent position to thereby substantially nullify the effect ofthercounterbalancing means when the extension lip is in said position. Yv 11. In an adjustable dockboard, the structure of claim 1Qfurther,characterizedby, Y

lip Vlifting means operatively connected with said moment arm-formingpart and the ramp and operable in consequence of movement of the ramp inonedirec- Ytion aboutits hinge connection with the mounting structurertoVsimultaneously move the moment arm away from a dead center position andwith the help ofthe counterbalancing means lift the extension lip towardits elevated position. 12. The structure of claim 1l wherein it iselevation of part of said connecting means forming a moment i3 the. rampwhich eects said operation of the lip lifting means, and furthercharacterized by,

manually controllable means to raise the ramp about its hingedlysupported rear edge.

13. In an adjustable dockboard of the type wherein a ramp having frontand rear edges has its rear edge hingedly supported so that the ramp mayswing up and down about its rear edge, and has an extension liphingedlyconnected to its front edge for movement between. a pendent positionwith respect to the ramp and an elevated position forming substantiallyan extension of the ramp, the improvement which comprises:

(A) a crank arm mounted on the ramp to swing in a plane normal to thehinge axis of the extension lip;

(B) means providing a motion transmitting connection between the crankarm and the extension lip through which (1') movement of the crank armin one direction raises the extension lip, and

('2) whereby the crank. arm occupies a predetermined position withrespect to the ramp when the extension lip is in its pendent positionwith respect to the ramp;

(C.) releasable lip supporting means on the ramp operable to support.the extension lip in an intermediate position short of its fullyelevated position when the lip has been lifted to said intermediateposition;

(D) means to counterbalance a;portion,of the gravityproducedv moment ofthe extension lip about they hinge connection with the ramp;

(E) means operatively connecting the counterbalancing means with theramp and with the crank arm and through which the eounterbalancing meansacts to impart anV increasing lip lifting torque to the extension lip asthe crank arm moves in one direction away from its said position, butsubstantially no lip lifting torque when the crank arm is in saidpredetermined position; and

(F) manually controllable means operatively connected with the crank armand the extension lip to (1) move the crank arm out of saidpredetermined position in said direction to lift the extension lip and(2) with the help ofthe counterbalancing means to lift the extension lipfar enough towards its elevated position to enable the lip supportingmeans to become operative.

14. In an adjustable dockboard of the type wherein a ramp having frontand rear edges has its rear edge hingedly connected to stationarysupporting structure so that the ramp may swing up and down about itsrear edge, and has an extension lip hingedly connected to its front edgefor movement between a pendent position with respect to the ramp and anelevated position forming substantially an Y extension of the ramp, theimprovement which comprises:

(A) manually controllable biasing means reacting between the stationarystructure and the ramp to swing the ramp upwards when said biasing meansis released, with a force which can be overcome by the application ofweight upon the ramp, so that the ramp may be lowered;

(B) a bell crank lever pivotally mounted at the front edge portion yofthe ramp to swing in a plane normal to the hinge axis of the extensionlip, one arm ot the bell crank lever bearing against the underside ofthe extension lip, the other arm of the hell crank lever extending alongthe Vunderside of the ramp when the extension lip is in its pendentposition with respect to the ramp, so that a downward pull on said otherarm lifts the extension lip;

(C) a snap line having one end connected to the stationary structure andits other end connected to said other arm of the bell crank lever toimpart a downward pull thereon as the ramp rises; and

f (D) lip counterbalancing spring means reacting between the ramp andsaid other arm of the bell crank lever to partially support thegravity-produced moment of the extension li'p about its hinge connectionwith the ramp and thereby enable a reduction in the force of the biasingmeans neededto raise the ramp and lift the extension lip.

l5. In an adjustable dockboard, the structure of claim 14, wherein f (A)said spring means is a compression spring;

wherein (B) one end of the compression spring bears against an abutmentxed to the underside of the ramp; and wherein (C) the other end of thecompression spring is connected with the bell crank lever at a pointwhich is so disposed with respect to thethrust axis of the spring whenthe extension lip is in its pendent position that the spring impartssubstantially no lip-lifting torque to the bell crank lever, y

so that the counterbalancing spring does not tend to move the extensionlip out of its pendent position but is increasingly etective tocounterbalance the gravity-produced moment of the extension lip thesameafter initial lip lifting motion has been imparted to the bell`crank lever.

16. In an adjustable dockboard, the structure of claim 15, furthercharacterized by:

(A) lip supporting means to support the extension lip in anintermediateposition short of its fully elevated position, said lipsupporting means comprising (1) an abutment xed with respect to theeXtension lip adjacent to its hinge axis,

(2) a pawl hingedly mounted at the front edge portion of the ramp inposition to have its free end engage said abutment and thereby supportthe extension lip when the pawl is in its operative position andtheextension lip has been raised high enough to carry said abutment pastthe free end of the pawl, p

(a) the pawl being biased to an inoperative position so that whenotherwise `unrestrained and the weight of the extension lip is removedfrom the pawl/the pawl assumes an inoperative position, and j (B) meansoperatively connected with the pawl and the stationary structure to movethe pawl to its operative position in consequence of elevation of theramp.

17. in an adjustable dockboard, the structure set forth in claim 16wherein the means for moving the pawl to its operative positioncomprises a tension spring connected between the pawl and said snapline;-

i. In an adjustable dockboard, the structure of claim 15, furthercharacterized by the fact that (A) the abutment which is xed to theunderside of the ramp and against which one end of the compressionspring bears, has a hole therethrough, and wherein i (B) the connectionbetween the other end of the compression spring and the bell crank levercomprises a rod pivotally connected at one end to the bell crank lever,

(1) the other end portionA of the rod being slidably received in saidhole in the abutment, and the rod passing lengthwise through thecompression spring, and

(2) an abutment adjustably mounted on said rod and against which saidother end of the cornpression spring bears.

19. The adjustable dockboard of claim t8, wherein the rod is threadedand the abutment on the rod against which the spring bears is a nutthreaded on the rod..

2t?. In an adjustable dockboard of the type wherein a ramp structurehaving front and rear edges has its rear edge hingedly connected withsupporting structure of the lip about its hinge axis.Y

so that the ramp may swing up and down`about its rear edge withrespecteto said supporting structure, and

` wherein the ramp structure has an extension lip hingedly connected toits front edge for movement betweena pendent position with respect totheramp and anfelevatedY position formingVv substantially anfextension ofthe ramp v to swing in a plane normal to the hinge axis of the s lip,between an operative and an inoperative position; v (B) means to movethe pivoted arm toits operative position; (C) means reacting between thepivoted arm and the lip whereby movement of the arm to and retentionthereof in its operative positionl supports the lip in" an elevatedposition, and whereby the gravityproduced moment ofthe lip about itshinge axis biases the pivoted arm toward its inoperative position anddescent of thelip entails movement of the armoutof its operativeposition;

(D) a stop member movably mounted on the ramp structureV at a pointspace d from the pivot axis of thearm for movement tol and from anoperative position; Y v l (E) force transmitting means connected withthe arm and cooperative with said stop .memberI when the latter is initsy operative position to support the arm in its operative position;and i (F) means connected with the stop member and operable to move Ythesame to its operative position.

Y`'21. The adjustable dockboard of claim Ztl, wherein the Y' means tomove the stop member is operatively connected between the stop memberand the stationary structure so asl to be responsive to relative motionbetween the said structures, whereby the stopV member is moved to itsoperative position in consequence of raising of the ramp structure. s

` 22. The adjustable dockboard ofl claim 2t), wherein 'the arm and thestop member arerin theiroperative positions, Y

27.'The adjustable dockboard of claim Z6, wherein Vthe front and rearend vportions of the rod means are relatively longitudinally movable,and spring means yieldingly urging the front and rear end portions ofthe rod means apart but yielding upon the application of force thereonin excess of that applied by the gravity-produced 'moment of theextended lip, so that upon the application of externalV force'on theelevated lip, the lip can fold down before the occurrence of damagethereto or its mounting. Y r

42S. In an adjustable dockboard of the type wherein a ramp structurehaving front and rear edges has its rear edge hingedly connected-witharsupporting structure so that the ramp structure may swing up and downabout the means tomove the pivoted arm to` its operative positioncomprises means connected between the arm and VtheV stationary structureand operableto translaterrelative motion between said structures intomovement' of the arm about its pivot, so that the arm is moved to itsoperative position in consequence o f raising of the ramp Astructure. Yl s s j 23. The adjustable dockboard ofrclaim Y2lb, wherein the means tomoverthe pivoted arm to itsoperativeY position and also the means to'move the stop member to itsvoperative position, are actuated byand areresponsive to relative motion between said structures.

24. The adjustable dockboard of claim 20, wherein s aid means whichreactsbetweenthe arm andthe lipv to support the lip constitutes, aforwardly directed projection on the arm to engage and lift the lip asthe arm moves to its operative position. Y

Y v25. The adjustable dockboard of claim 24,' further characterized byspring means reacting between portions oit the ramp structure and thepivoted armtwhich are spaced frornthe pivotaxis of the armtoimparttorque to the arm in` thexdirection'to lifttthe lip vand therebycounterbalance a portion of the gravity-produced moment j the'pivotedarm is located near the. trontedge of the its rear edge with respect tothe supporting structure, and wherein the ramp structure has anextension lip hingedly connected to its front edge for movementbetween apendent position with respect to the ramp and an elevated positionforming substantially an extension ofthe ramp structure, the improvementwhich comprises: (A) a crank arm pivoted to the front endportion of Ythe ramp structure to swing inV a plane normal to theV hinge axis of thelip between an inoperative rearwardly extending position and anoperative position directed. generally downwardly toward the supportingstructure; f

(B) means toY react between the crank arm and the lip and through whichmovement of the crank arm fromits inoperative to its `operativepositionlifts the lip to an elevated position, and retention of theycrank arm in its operative position supports the lip in said elevatedposition so that the gravity-produced moment ot the lip about its hingeaxis-biases the crank arm toward its inoperative position and descent ofthe lip entails movement of the crank arm out of its operative position;

( C) rod'means pivotally connected to theV outer end portion of thecrank armV and extending therefrom toward the -rear edge of the'rampstructure;

(D) means slideably supporting the rodrmeans for endwise fore andV aftmovement as the crank arm is swung on its pivot;V

(E) stop means movably mountedon the ramp structure for movement to anoperative position engageable with a part on the rod means `when thelatter has moved forward in consequence of lip elevating motion of thecrank arm, Yto hold the rod means against rearward motion and therebyholdthe crank arm in its lip supporting position;

(F) means vconnected with the crank arm for moving the llatter from itsinoperative to its operative position; and

(G) means connected with the stop means for moving the same to itsoperative position.

29. The adjustable dockboard of claim 28, wherein i the means for movingthe crank arm and` the stop means to theirV operative positions functionin consequence of relative motion between said structures as therampstrucv ture is'raised.

ramp structure and the stop member is remote from s the front edgethereof,'wherein the force transmitting means comprises rod means havinga front end portion pivotally connected to the arm and a rear endportion which moves back and forth asv the arm swings lon its pivot; andguide means onfthe ramp structure slidably supporting the rearendportion of the rod means in position for engagement with the stopmember when 30. The adjustable dockboardV of claim 28, furthercharacterized by a counterbalancing spring on said rod 6 means, reactingbetween a partV on the rod means and a part ixed with respect tothe rampstructure, to bias the rod means forwardly and thereby counterbalance aportion of the gravity-produced moment'of the lip about its hingeraxis.

3l. The adjustable dockboard of claim 28, wherein said rod meanscomprises telescopingly` connected front and rear sections, the

front section being connected with the crank arm and `the rear sectionbeing engageable with the stop means, a spring reacting between thetelescopingly connected sections urging the same apart, and means 17 18to limit the spring-produced separation of said secentiregravity-produced moment of the lip about its tions, so that saidsections act as one single unit as hinge axis, but yielding under forcegreater than that long as the force of said spring is not overcome.imposed thereon by said moment of the lip, so that 32. The adjustabledockboard of claim 31, further the sections of the rod means yieldiuglyapproach characterized by a second spring reacting between the 5 oneanother upon the application of external force front section of the rodmeans and an abutment fixed on the lip tending to push the same down.with respect to the ramp structure, to urge the rod means f0rward1y, Noreferences cited.

said springs together being capable of supporting the JACOB L NACKENOFPPfl-maw Examiner.

1. IN AN ADJUSTABLE DOCKBOARD OF THE TYPE WHEREIN A RAMP HAVING FRONTAND REAR EDGES HAS ITS REAR EDGE HINGEEDLY SUPPORTED SO THAT THE RAMPMAY SWING UP AND DOWN ABOUT ITS REAR EDGE, AND HAS AN EXTENSION LIPHINGEDLY CONNECTED TO ITS FRONT EDGE FOR MOVEMENT BETWEEN A PENDENTPOSITION WITH RESPECT TO THE RAMP AND AN ELEVATED POSITION FORMINGSUBSTANTIALLY AN EXTENSION OF THE RAMP THE IMPROVEMENT WHICH COMPRISES:(A) ENERGY STORING MEANS TO COUNTERBALANCE A PORTION OF THEGRAVITY-PRODUCED MOMENT OF THE EXTENSION LIP ABOUT ITS HINGE CONNECTIONWITH THE RAMP (B) MEANS OPERATIVELY CONNECTING THE ENERGY STORING MEANSWITH THE RAMP; AND (C) MEANS OPERATIVELY CONNECTING THE ENERGY STORINGMEANS WITH THE EXTENSION LIP, WHEREBY THE ENERGY STORING MEANS REACTSBETWEEN THE RAMP AND THE EXTION LIPTO IMPART LIFTING TORQUE TO THEEXTENSION LIP, SAID LAST NAMED MEANS INCLUDING STRUCTRUE HAVING A MOMENTARM THROUTH WHICH THE ENERGY STORING MEANS EXERTS ITS COUNTERBALANCINGFORCE UPON THE EXTENSIO LIP, MOVEMENT OF THEEXTENSION LIP TO ITS PENDENTPOSITON MOVING SAID MOMENT ARM INTO SUBSTANTIALLY ITS DEAD CENTERPOSITON TO THEREBY SUBSTANTIALLY NULIFY THE EFFECT OF THE ENERGY STORINGMEANS UPON THE EXTENSION TO RENDER THE COUNTERBALANCING EFFECT OPERATIVETO RENDER THE COUNTERBALANCING EFFECT OF THE ENERGY STORING MEANS UPONTHE EXTENSION LIP INCREASINGLY EFFECTIVE AS THE EXTENSION LIP MOVES FROMSAID PENDENT POSITION TOWARDS ITS ELEVATED POSITION.